Introduction
Physocephala have an petiolate abdomen with segment 2 long and narrow, the others broader and shorter. They resemble solitary wasps. Adults are frequent flower visitors, that are found on Composites, Umbellifers &c. Their larvae are endoparasites of Sphecidae, bees, bumble bees and social wasps.
Key
1.b. Side of thorax with silverish stripe, from the implant of the wing to the base of leg 2 -> 5
2.a. Face below antennal implant with a black stripe, above the antennal implant partly blackish -> 3
2.b. Face yellow, without black stripe below and blackish parts above antennal implant 9-16 mm. NL, B, D. -> Physocephala vittata Fabricius
3.a. Face: black stripe below antennal implant rounded at its lower end; antennae blackish; hind edges of tergites 3-5 with wide, indistinqtly delimited dust bands which are clearly broader in the middle -> 4
3.b. Face: black stripe below antennal implant deeply forked into two arms; antennae red; femur uniformly reddish; hind edges of tergites 3-5 with narrow, clearly delimited dust bands of even width. 15-20 mm. NL, B, D. -> Physocephala nigra DeGeer
Head of P. rufipes, with black stripe rounded below and P. nigra, with black stripe forked below.
5.a. Wing: dark stripe does not directly border the front margin of the wing over its full length, the first wing cell whitish, hyaline or only weakly coloured, the dark stripe may almost lack; legs red, orange of yellow-red, base of tibia turning whitish -> 6
6.a. Wing: dark stripe strong and well marked, in addition a dark spot at the wing tip; antennae black; abdomen: black with red parts on tergites 2-3, yellowish dust bands at the hind margin of all tergites; legs red. -> 7
6.b. Wing: dark stripe almost lacking and not well marked, no dark spot in wing tip; antennae red to red-brown; abdomen: in females largely redbrown, in males largely blackish, with yellowish dust bands at the hind margins of all tergites; legs yellow-red. 11-16 mm. -> Physocephala variegata Meigen
 
Stuke J.-H. 2005. Bestimmung und Taxonomie der palaarktischen Conopiden (Diptera) 1. Teil: Die Physocephala rufipes-Artengruppe. Studia dipterologica 12: 369-384.
Van Veen M. 1984. De Blaaskopvliegen en roofvliegen van Nederland en België. Jeugdbondsuitgeverij, Utrecht.